Mold for casting monolithic spherical tanks



March 24, 1953 A. R. ANDERSON 2,632,226

MOLD FOR CASTING MONOLITHIC SPHERICAL TANKS Filed Aug. 18, 1949 2 SHEETS-SHEET 1 jaw.

\ALL lllllllill INVENTOR. ARTHUR R. ANDERSON March 24, 1953 A. R. ANDERSON 26 MOLD FOR CASTING MONOLITHIC SPHERICAL TANKS Filed Aug. 18, 1949 2 SHEETSSHEET 2 37 29 a4 a5 5/ J0 VIIIIIIIIl II/I '1 III III III IN V EN TOR.

:RTHUR R. A/vamswv B AT RNEY Fatented Mar. 24, 1953 as easier rare MOLD FOR CASTING MONOLITHIC SPHERICAL TANKS Arthur R. Anderson, Tacoma, Wash.

Application August 18, 1949, Serial No. 111,037

Summary of the invention In accordance with my invention, a mold for casting monolithic tanks of generally spherical form comprises an inner mold assembly made up of structural segments removably secured together, an outer mold assembly made up of structural segments removably secured together, and removable spacing elements constructed and arranged to support the inner mold assembly in spaced relationship to the outer mold assembly. The structural segments of the inner mold assembly are of arcuate tapering form, and the removable spacing elements comprise a pair of members extending from the bottom of the mold to an opening in the top of the mold, and a fastening adjacent the opening for fixing the position of these members relative to one another. Plates at the bottom of the mold provide securing and clamping means for the inner and outer mold segments.

One of the spacing elements is retractable during the casting operation to permit flow of cast material into the space first occupied by said spacing element whereby the tank is of monolithic construction and has walls devoid of seams or openings except at its top.

The arcuate tapering segments of the inner mold assembly preferably have inwardly extending flanges along their meeting edges, and resilient strips between these flanges permit contraction as the cast material solidifies. Tensioning bands inside the inner mold assembly pull the segments tightly together.

The spacing and securing means are readily dismantled, and the inner mold segments are removable through the small opening left in the top of the monolithic tank.

It has been proposed heretofore to approximate a monolithic concrete spherical tank construction by first casting a foundation slab and then inflating a fabric bag which is then covered with cement by spraying or trowelling. The fabric bag is left in place to make the container impervious to the liquid which the tank is designed to hold. This tank is of course not monolithic, because of the joint between the pro-cast foundation slab and the upper part of the tank. In general, the prior art has taught making tanks by casting or otherwise forming one section at a time. Removable inner mold segments have been suggested, but the floor or lower part of the tank always had to be formed as a separate operation. This meant that there would always be a seam or joint where the concrete laid or cast in the separate operations came together. It has been a leading object of my invention to eliminate this difficulty, and to provide a true monolithic cast construction without seams, joints, fabric liners or anything of that sort.

Description In the drawings, wherein I have illustrated what I now consider to be the preferred form of my invention:

Fig. l is a side elevational view of the mold and molded container, partly broken away in central vertical cross-section, and with the upper centering and retaining members removed.

Fig. 2 is a plan view of the same, partly broken away in central horizontal cross-section, with the upper and lower centering and retaining members removed.

Fig. 3 is an enlarged vertical cross-sectional view of the upper portion of the mold and molded container before removal of the centering and retaining members; and Fig. 4 is a similar view of the lower portion of the mold and molded container.

Fig. 5 is an enlarged partial central horizontal sectional view of the inner mold, showing one of the tensioning elements and the collapsible key section of the inner mold.

Fig. 6 is a detail view looking at the inside of the inner mold and showing in front elevation the retaining means for the two parts of the collapsible key section.

Fig. 7 is a detail perspective view of one of the devices for applying tension to the cables inside of the inner mold.

Fig. 8 is a central vertical cross-sectional view of one form of top closure for the molded container.

Referring to Figs. 1 and 2, my improved mold apparatus in its general arrangement comprises an inner mold assembly 9 and an outer mold assembly Iii. In the specific construction shown, the inner mold assembly is made up of twelve structural segments H which are of arcuate tapering form (or of a form which might be likened to that of an orange peel). Along their meeting edges these segments have inwardly extending flanges such as those provided by the inwardly extending legs of angle irons i2 welded or otherwise fixed to the marginal edges of the segments. I have found that some practical advantages are obtained by departing slightly from a true spherical form as in the construction shown. Here each segment is made of two complementary sections l3 of cylindrical form tapering toward their ends. Sections [3 can be blanked out separately, rolled to cylindrical form and welded together where they meet at it, or, alternatively, segments H can be formed in one piece in a press. In either case, since the meeting sections of adjacent segments lie in common cylindrical surfaces, the inwardly extending legs of angle irons l2 can be arranged normal to these surfaces. Thus right angle irons can be used without special deformation other than to roll them into a curved form to match the cylindrical form of the meeting sections of segments l l. The meeting edges of segments II and the meeting edges of sections l3 are arcs of great circles of a sphere.

In my preferred construction the outer mold assembly is made up of four structura} segments l5 substantially conforming to the shape of the inner mold assembly but slightly larger so as to provide a casting cavity between the two mold assemblies, the spacing between them being designed to produce a cast body of the desired wall thickness. Segments are made up of a series of sections of cylindrical form tapering toward their ends as described in connection with segments ll of the inner mold assembly. As shown, each segment 15 has four cylindrical sections. The meeting edges of these segments are flanged or are bound with angle irons l6 by which they are secured together with bolts l1.

Referring to Figs.3 and 4,1 will now describe the fastening elements for securing the ends of the segments together, and the removable spacing elements associated therewith for holding the inner and outer mold assemblies in predetermined spaced relationship. The removable spacing elements comprise a pair of members extending from the bottom of the mold to an opening in the top of the mold. These members, in the embodiment illustrated, consist of a tubular element l8 and a post l9. An inner center bottom plate holds the lower ends of segments II which are flanged upwardly and inwardly at 2| to abut and overlie this plate. Tubular element [8 fastens to the plate 20, as by a screw threaded engagement 22, and extends upwardly therefrom through the center of the mold. A clamping plate 23 is welded or otherwise fixed to tubular element 18, and upon tightening the aforesaid screw threaded connection serves to clamp flanges 2| of the lower ends of segments H between plates 26 and 23. An outer center bottom plate 24 holds the lower ends of the segments l5 of the outer mold assembly. These preferably are flanged downwardly at 25 and have marginal ring segments or lugs 26 welded to them to receive stud bolts 2! extending through plate 24 to secure the segments l5. Post I9 fastens to plate 24, as by a nut 23 engaging the reduced threaded end of the post, and extends upwardly therefrom through tubular element l8. A fastening pin 29 extends through aligned apertures in the post and tubular element near the top of the mold to hold them against relative movement thereby supporting the bottoms of the inner and outer mold assemblies in predetermined spaced relationship.

Fig. 3 also shows fastening elements for securing the upper ends of the inner and outer se ments, these elements engaging tubular element l8 to center the upper ends of the inner and outer mold assemblies. In my preferred construction these fastening elements consist of the follow ing: first, for the inner segments, there is a hoop 30 which is slipped over the upwardly flanged ends 3| of segments H, a split ring 32 which has a flange at the top to overlie hoop 30, sleeves 33 fixed to ring 32, threaded rods 34 slidably engaging sleeves 33 with adjusting nuts 35 on the rods, and center plate 35 to which the rods are fixed. Plate 36 has a central aperture to slidably receive tubular element l8. When nuts 35 are tightened against the ends of their respective sleeves 33, split ring 32 clamps the flanged ends of segments ll between it and hoop 33. Second, for the outer segments, there is a ring 3'1 having a central aperture for element l8 and threaded to receive bolts 38 the ends of which engage brackets 39 fixed to the upper ends of segments l5. These fastenings for the upper ends of the inner and outer mold segments cooperate with spacing member l8 to center the upper ends of the inner and outer mold assemblies and insure, in conjunction with spacing member 19, a uniform wall thickness of the body to be cast while at the same time permitting that body to be formed in a single casting operation so as to produce a true monolithic structure devoid of seams and without any form of spacer being left within the casting. Resilient strips [4 of soft rubber or the like permit a certain amount of contraction of the inner mold as the cast material sets up. Ihese strips may be cemented or otherwise attached to one of each pair of complementary angle irons l2. Post I9 is retractable through tubular element l8 after the body has been cast whereby the space between the inner and outer center bottom plates 20 and 24 can be completely filled through flow of the cast material before it has set.

Tensioning bands or cables 40 (Figs. 3, 4 and 5) arranged inside the inner mold assembly engage a series of hooks 4| on angle irons I2 to pull the segments ll tightly together. I prefer to use three such tensioning bands, two located as shown in Figs. 3 and 4, and a third located at the mid-section, or equator. A toggle clamp 42 such as shown in Figs. 5 and '7 may be used to tighten the bands 40. Other well-known means, such as a turnbuckle, could be used instead.

Mold segment H (Fig. 5) constitutes a key section to facilitate stripping the inner mold assembly at the conclusion of the casting operation, 1. e. after the cast material has set up sufficiently to retain its form. This key section is made in two parts 43, 44, part 44 having an offset flange 45, and the two parts being held apart by a spacing bar or bars 46 removably bolted to lugs 5'! fixed to the respective parts. The inner mold segments I l, l I, having been forced tightly together by the tension in bands 43 and any shrinkage of the cast body, are relieved of pressure by first removing key section I l which col lapses readily as soon as spacer bar or bars 46 are removed. Thereafter parts 44 and 43 are withdrawn through the opening in the top of the cast tank, and the remaining segments II are also withdrawn. The maximum width of segments ll, and consequently the number of such segments, is so selected in relation to the size of the opening in the top that the segments can be readily withdrawn. The top opening can be finished off with the use of a trowel after the concrete or other material has been cast. Also, a split band 48 (Fig. 3) can be used to help in molding the edge of the opening to the desired form and reduce the amount of hand trowelling required.

Cover section 59 (Fig. 8), with pipe connections 50, can be formed in a conventional mold and sealed into the tank opening with a suitable gasket or plastic sealing compound forced into complementary recesses in the edges of the container opening and cover.

Operation In assembling the mold, I have found it convenient to use a roughly circular wooden form which is of such a size and so disposed as to loosely support the inner mold segments as they are assembled one by one. I begin by assembling tubular element I8 with inner center bottom plate 20, not screwing it all the way in but leaving a little extra clearance between plates 29 and 23. This sub-assembly is next set upright in the center of my circular wooden form, and one by one I set up the segments H with their lower flanges 21 going in between the plates and 23. After all inner segments are so set in place I turn element It to clamp flanges 2i between plates 26 and 23, then reach inside through the top opening and drop lower tensioning cable 40 over the lower set of hooks 4| and tighten it by snapping home the toggle 52. In similar fashion I insert and tighten next the intermediate tensioning cable, and finally the upper one (asy plate 36, rods 39, sleeves 33 and split ring 32, 3

after which I tighten nuts 35. This completes assembly of the inner mold.

Post 19 is now keyed in place with pin 29 and with outer center bottom plate 24 secured by nut 28. sembled before setting up the inner mold segments.) With top ring 3'! in place, I next erect the outer mold segments l5 one by one, each being secured in turn by stud bolts 21 at the bottom and spacer bolts 38 at the top. Finally, the segments l5 are secured to one another at their meeting edges by the bolts ET. This completes assembly of the entire mold.

The mold is now filled with the material from which the tank or other container body is to be made. The material, in a liquid or plastic state is poured into the mold through the annular space between the inner and outer mold assemblies at the top. If a sufiiciently plastic material such as concrete is used, the post l9 can be raised immediately after filling the mold, allowing the space between plates 20 and 24 to be completely filled. To avoid leakage, the hole in plate 24 can be plugged. The boundary of the opening at the top of the container can be formed with the metal ring d8, or the plastic material can be trowelled to the desired design.

After the material cast has set up sufficiently to hold its form, the mold is ready to be taken apart. Bolts 2'! and 38 are removed, and outer segments l5 stripped away. Top retaining means are removed after nuts have been loosened. Tubular element i8 is unscrewed from plate 20 and removed. Toggles 42 are released and tensioning cables unhooked and lifted out through the top opening. Spacing bars 46 are then unbolted, permitting collapse of key section H, the parts 44 and 43 of which are then withdrawn through the top opening, after which segments H are likewise withdrawn one by one.

(If desired these members can be as- Plate 20 is removed and the mold is now ready for re-use in molding another container, subject to any necessary cleaning.

It will be understood that the shape of the container which can be cast with the mold apparatus I have described is subject to considerable variation. It can be a true sphere, an ellipsoid of revolution, a many-sided polygon approximating a sphere, or a modified spherical approximation as illustrated herein. Consequently the invention is applicable to molds for casting all kinds of hollow monolithic bodies which are of generally spherical form or substantially spherical, and the expression of generally spherical form as used herein and in the appended claims is to be understood as comprising such variants as I have indicated herein and other forms which properly can be regarded as substantial equivalents. The terms and expressions which I have employed are used in a descriptive and not a limiting sense, and I have no intention of excluding such equivalents of the invention described, or of portions thereof, as fall within the purview of the claims.

I claim:

1. A mold for casting monolithic tanks of generally spherical form comprising inner and outer mold assemblies made up of arcuate tapering segments, fastening elements for securing the ends of the segments together, and removable spacing elements associated with said fastening elements to hold the inner and outer mold assemblies in spaced relationship, said removable spacing elements comprising a pair of members extending centrally through the mold from the bottom of the mold to an opening in the top of the mold and a fastening adjacent the opening for fixing the position of said pair of members relative to one another to predetermine the aforesaid spaced relationship between the inner and outer mold assemblies.

2. A mold for casting monolithic hollow bodies of generally spherical form comprising an inner mold assembly made up of arcuate tapering segments, an inner center bottom plate for holding the lower ends of said segments, a tubular element which fastens to said plate and extends upwardly therefrom through the center of the mold, an outer mold assembly made up of segments, an outer center bottom plate for holding the lower ends of said outer segments, a post which fastens to said outer plate and extends upwardly therefrom through said tubular element, and a fastening for holding said post and w bular element against relative movement thereby supporting the bottoms of said inner and outer mold assemblies in predetermined spaced relationship.

3. A mold for casting monolithic hollow bodies of generally spherical form comprising an inner mold assembly made up of arcuate tapering segments, an inner center bottom plate for holding the lower ends of said segments, a tubular element which fastens to said plate and extends upwardly therefrom through the center of the mold, an outer mold assembly made up of segments, an outer center bottom plate for holding the lower ends of said outer segments, a post which fastens to said outer plate and extends upwardly therefrom through said tubular element, a fastening for holding said post and tubular element against relative movement thereby supporting the bottoms of said inner and outer mold assemblies in predetermined spaced relationship, and fastening elements for securing theupper ends of'said inner and outer segments,

said fastening elements engaging said tubular element to center the upper ends of the inner and outer mold assemblies.

4. A mold for casting monolithic hollow bodies of generally spherical form comprising an inner mold assembly made up -of arcuate taperingse'gments, an inner center bottom plate for holding the lower ends of said segments, a tubular element which fastens to'said plate and extends upwardly therefrom through the center of the mold, an outer mold assembly made up of segments, an outer center bottom plate for holding the lower ends of said outer segments, a post which fastens to said outer plate and extends upwardly therefrom through said tubular element, a fastening for holding said post and tubular element against relative movement thereby supporting the bottoms of said inner and outer mold assemblies in predetermined spaced relationship, and a clamping plate'fixed to said tubular element adjacent the inner center bottom plate, the tubular element having a screw threaded engagement with the last-named plate whereby the lower ends of the inner segments can be clamped between the two last-named plates by turning the tubular element after the inner segments have been assembled.

5. A mold for casting monolithic hollow bodies of generally spherical form comprising an inner mold assembly made up of arcuate tapering segments, an inner center bottom plate for holding the lower ends of said segments, a tubular element which fastens to said plate and extends upwardly therefrom through the center of the mold, an outer mold assembly made up of segments, an outer center bottom plate for holding the lower ends of said outer segments, a post which fastens to said outer plate and extends upwardly therefrom through said tubular element, a fastening for holding said post and tubular element against relative movement thereby supporting the bottoms of said inner and outer mold assemblies in predetermined spaced rela- 8 tionship, and said post being'retractable through said tubular element after the body has been cast whereby the space between the inner and outer center bottom plates can be completely filled through flow of the cast material before it has "set.

6. A mold for casting tanks of generally spherical form comprising inner and outer mold assemblies made up of inner and outer arcuate tapering segments, fastening elements for securing the ends of the inner segments together and for securing the ends of the outer segments together, and spacing elements associated with said fastening elements to hold the inner and outer mold assemblies in predetermined spaced relationship, one of the spacing elements being removable during the casting operation to permit flow of cast material into the space first occupied by said spacing element whereby the tank is of monolithic construction and has walls devoid of seams or openings except at its top.

ARTHUR R. ANDERSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

